1. Field of the Invention
The present invention relates to a chemically amplified positive photoresist composition for thick film, a thick-film photoresist laminated product, a manufacturing method for a thick-film resist pattern, and a manufacturing method for a connection terminal. More specifically, the present invention relates to a chemically amplified positive photoresist composition for thick film, a thick-film photoresist laminated product, a manufacturing method for a thick-film resist pattern, and a manufacturing method for a connection terminal which are ideal for use in the formation of connection terminals such as bumps or metal posts, and wiring patterns, during both the manufacture of circuit substrates, and the manufacture of electronic components such as CSP (chip size packages) that are mounted on such circuit substrates.
2. Description of Related Art
Photofabrication, which is now the most widely used technique for precision microprocessing, is a generic term describing the technology used for manufacturing precision components such as semiconductor packages by applying a photosensitive resin composition to the surface of a processing target to form a coating, patterning this coating using photolithography techniques, and then conducting chemical etching or electrolytic etching, and/or electroforming based mainly around electroplating, using the patterned coating as a mask.
Recently, reductions in the size of electronic equipment have lead to further developments in higher density packaging of semiconductor packages, including multipin thin-film packaging, reductions in package size, two dimensional packaging techniques using flip-chip systems, and other improvements in packaging density based on three dimensional packaging techniques. In these types of high density packaging techniques, connection terminals, including protruding electrodes (mounting terminals) such as bumps which protrude above the package, and metal posts that connect rewiring extending from peripheral terminals on the wafer with the mounting terminals, must be positioned on the surface of the substrate with very high precision.
The materials used in the above type of photofabrication are typically thick-film photoresists. Thick-film photoresists are used for forming thick-film photoresist layers, and can be used, for example, in the formation of bumps or metal posts by a plating process. Bumps or metal posts can be formed, for example, by forming a thick-film photoresist layer with a film thickness of approximately 20 μm on top of a support, exposing the photoresist layer through a predetermined mask pattern, developing the layer to form a resist pattern in which the portions for forming the bumps or metal posts have been selectively removed (stripped), embedding a conductor such as copper into the stripped portions (the resist-free portions) using plating, and then removing the surrounding residual resist pattern.
Positive photosensitive resin compositions including a compound containing a quinone diazide group have been disclosed as suitable thick-film photoresists for the formation of bumps or wiring (for example, see patent reference 1).
On the other hand, chemically amplified photoresists including an acid generator are known as photosensitive resin compositions with even better sensitivity than that provided by conventional positive photosensitive resin compositions including a compound containing a quinone diazide group. The characteristic features of a chemically amplified photoresist are that on irradiation (exposure), acid is generated from the acid generator, diffusion of this acid is promoted by post exposure baking, and the base resin or the like of the resin composition then undergoes an acid-catalyzed reaction, thereby altering the alkali solubility of the reacted resin.
Chemically amplified photoresists include positive photoresists, in which irradiation causes alkali insoluble portions to become alkali soluble, and negative photoresists, in which irradiation causes alkali soluble portions to become alkali insoluble. Of these two types, as positive photoresists, chemically amplified photoresist compositions for plating have already been disclosed (for example, see patent reference 2 and patent reference 3).
Requirements for the type of thick-film photoresist composition described above include an ability to form a film thickness of at least 10 μm, favorable adhesion to substrates, favorable resistance to the plating solution and favorable wetting characteristics in the plating solution during the plating treatment used for forming bumps, good conformation of the metal composition formed by the plating treatment to the resist pattern shape, and an ability to easily strip the photoresist using a stripping solution following the plating treatment. Furthermore, with advances in plating technology, multiple plating steps and plating steps that require more severe conditions have become necessary, meaning the photoresist also requires favorable resistance to the plating process itself, to enable it to withstand multiple plating steps.
(Patent Reference 1)    Japanese Unexamined Patent Application, First Publication No. 2002-258479
(Patent Reference 2)    Japanese Unexamined Patent Application, First Publication No. 2001-281862
(Patent Reference 3)    Japanese Unexamined Patent Application, First Publication No. 2001-281863
However, when conventional chemically amplified photoresist compositions disclosed in the patent references 2 and 3 are used to produce a thick-film resist layer, because the stress resistance of the photoresist composition to the plating process is unsatisfactory, the metal layer obtained from the plating treatment tends to swell, making it difficult to achieve a favorable pattern for the plated product. Furthermore, the resistance of the photoresist composition to the plating solution is also inadequate, with chips and cracks developing in the resist either during the plating step or during the washing step following plating, making conducting multiple plating steps with the same resist pattern essentially impossible (poor plating resistance).
Furthermore, with the photosensitive resin composition comprising a compound containing a naphthoquinone diazide group disclosed in the patent reference 1, which displays superior plating resistance, improving the sensitivity is problematic.